# Data Tunnels

Services are reachable only through authenticated channels, preventing unauthenticated scanning and external access.

| Property            | Traditional Network          | Enigma Tunnels                      |
| ------------------- | ---------------------------- | ----------------------------------- |
| **Discoverability** | Services announce themselves | Nothing visible until authenticated |
| **Routing**         | Stable paths, cacheable      | Paths change every epoch            |
| **Endpoints**       | Fixed IPs, known ports       | No exposed endpoints                |

The pseudocode below illustrates the high-level steps used to establish an authenticaed tunnel.

```angular-ts
// TUNNEL ESTABLISHMENT PSEUDOCODE

function establishTunnel(user, targetService):
    // Phase 1: Authentication (BEFORE any network access)
    identity = user.getCertificate()
    if not verifyIdentity(identity):
        return REJECT  // No unauthenticated access

    // Phase 2: Policy Check
    policy = controller.getPolicy(identity, targetService)
    if not policy.allows(identity, targetService):
        return UNAUTHORIZED

    // Phase 3: Route Calculation (epoch-dependent)
    currentEpoch = getCurrentEpoch()
    availableRouters = getRoutersForEpoch(currentEpoch)
    route = calculateRoute(user.location, targetService, availableRouters)

    // Phase 4: Session Key Derivation
    ephemeralKey = generateECDHKeyPair()
    sessionKeys = deriveSessionKeys(ephemeralKey, targetService.publicKey)

    // Phase 5: Encrypted Tunnel
    tunnel = createEncryptedChannel(route, sessionKeys)

    return tunnel

function onEpochBoundary(tunnel, newEpoch):
    // Route rotation without dropping connection
    newRoute = calculateRoute(tunnel.user, tunnel.service, newEpoch)
    tunnel.migrateRoute(newRoute)
    tunnel.rotateSessionKeys()  // Forward secrecy
```


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